Work control mechanism for machine tools



May 13, 1947. B. s. T. BlsHoP T AL WORK CONTROL MECHANISM FOR MACHINETOOLS 4 Sheets-Sheet 1 Filed June 8, 1944 i:- Ei

May 13, 1947. B. s. T. BISHOP ET AL 2,420,296

l WORK CONTROU MECHANISM FOR `MACHINE TOOLS l L Filed June a, 1944 4sheets-sheet 2 Inveno'rs,

May 13, 1947.

B. s. T. BISHOP x-:TAL 2,420,296

WORK CONTROL MECHANISM FOR MACHINE TOOLS` Filed June 8, 1944 4Sheets-Sheet I5 May 13, 1947. B 'SQ T, BISHOP ET 'AL 2,420,296

` WORK CONTROL MECHANIjsMpoR MACHINE TooLs Filed June 8, 1944 v 4sheets-sheet 4 Patented May i3, yi947 STATES PATENT OFFICE WRK CONTROLMECHANISM FOR, MACHINE TOOLS Application .lune 8, 1944, Serial No.539,356

2 Claims.

This invention relates to improvements in machine tools of the generalclass wherein the work is held between headstock and tailst-ock centersand is rotated while being fed past a cutting or other tool which is toperform a particular operation upon the work at a predetermined locationat which the tool can be adjusted into and out of operative relation tothe work.

Our invention is herein illustrated and described in connection with athread grinding machine, but it should 'oe understood that the novelfeatures disclosed are applicable to machine tools of variousdescriptions wherein the work is held between centers and moved axiallypast a tool.

Machine tools of the mentioned general class require interconnection ofthe headstock and tail stock spindles so that the spindles, and theworkholding centers therein, can move in unison as the work is being fedpast the tool.

It is among the objects of our present invention to provide improvedmeans for ensuring unitary axial travel of the head and tail stockspindles and ensuring also an approximate uniformity of axial pressureupon the work between centers throughout the complete range of travel ofthe work relative to the cutting wheel or other tool, and upon each ofsuccessive similar work pieces inserted between the centers. We employ aconstruction in which the head and tail stock spindles move axiallywithin their respective stocks when feeding the work past the cuttingwheel, and in which the interconnection between the spindles is acushioned interconnection which is adjustable to provide a suitableaxial pressure on the Work and which automatically maintains thatpressure uniform.

Another object of our invention is to embody Within the headstock themeans for axial movement of the spindles, and to provide a flexibledrive for rotating the headstock spindle which permits axial travel ofthe spindle while the source of power continues relatively stationary. Ascrew on the headstock spindle, coacting with a nut fixed interiorly ofthe headstock, causes axial movement of the spindle when the spindle isrotated, and a V-belt drive connection between the spindle and the powersource permits this axial travel of the spindle while the power source,such as a reversible electric motor, remains lixed in position.

Another object of our invention is to provide means for automaticallystopping the work-driving motor at each predetermined limit of axialtravel of the work holding spindles, to the right and to the left. Apair of spaced apart microswitches are controlled by movements of theheadstock spindle so that, at a predetermined limit of travel of thespindle to the right, one micro-switch in the motor circuit is opened,and, at a predetermined limit of travel of the spindle to the left, theother micro-switch in the motor circuit is opened. By providing so thateach micro-switch is reclosed shortly after the means which opened itmoves away, a manual threeposition switch having a left position, acentral olf position, and a right position can control the work-drivingelectrical system.

Still another object of our invention is to provide means whereby thetailstock spindle, when engaging a piece of work, is free to be movedmanually away from the work for removal of the work, and automaticallyengages a newly inserted lwork piece with the predetermined pressurethereon, when released from a manually retracted position. Thepreviously mentioned cushioned interconnection between spindles permitsmanual resilient retraction of the tailstock spindle without movement ofthe headstock spindle, and the tailstock spindle, when released, ismoved back into engagement with a work piece by the resilience of abacking spring or the like in the said interconnection.

A further object of our invention resides in the ball bearing mountingstructure for the headstock and tailstock spindles, whereby they areaxially and rotatably movable within their stocks.

It is, moreover, our purpose and object generally to. improve thestructure and operation of thread grinding machines.

In the accompanying drawings:

Figure 1 is a front elevation of a thread grinding machine embodyingfeatures of our invention;

Figure 2 is an end elevation looking from the left in Figure l;

Figure 3 is a vertical medial sectional view of the headstock, on alarger scale;

Figure 4 is a vertical medial sectional view of the tailstock on thesame scale as Figure 3;

Figure 5 is an end elevation of the tailstock, looking from the right inFigure 4;

Figure 6 is a sectional view on line '--S of Figure 1;

Figure 7 is a sectional View on line 'l-l of Figure 1;

Figure 8 is a sectional view online 8-8 of Figure 3;

Figure 9 is a fragmentary sectional view of one of the ball bearingunits employed in both headstock and tailstock;

Figure 10 is a iront elevation looking into the 3 micro-switch casings,the front covers being removed;

Figure 11 is a sectional View on line II-II of Figure l; and

Figure 12 is a diagrammatic representation of the electricalconnections.

Referring to the drawings, the machine bed is formed at its forward topportion with a longitudinally extending plane horizontal surface I2 onwhich is secured the base member I4 for supporting both the headstock I5and the tailstock I8. The base member may be secured on surface I2 inany suitable manner as by the bolts 2i?. The headstock I6 and tailstockI8 are secured in longitudinally adjustable relation on the base memberI4, as by the T-bolts 22 engaging a T-slot 24 in the base member andretained by the nuts 23 on the ends of the T-bolts. The headstock I6 andtailstock I3 remain fixed in position after they have been adjusted andsecured on base member I4 for any particular work-threading operation.

The work (not shown) is held between the centers 28, 33, respectively,in the lieadstock spindle 32 and the tailstock spindle 34, and isrotated by its engagement with the driven headstock center 26.

According to our present invention, the headstock spindle 32 has securedthereon, within the headstock, an exteriorly screw-threaded sleeve 3Swhose threads 38 are the same as the threads to be cut in the work. Asbest seen in Fig. 3, this master-thread sie-eve 36 may be keyed tospindle 32 as at 43, and is shown engaged endwise between the twospindle bearing bushings 42, 44, which in turn are clamped endwisebetween a shoulder 46 on spindle 32 and a pulley 48 keyed as at 5U tothe outer end of the spindle, and pressed against the end of bushing 42by nut 52 which is screw-threaded on the extreme outer end of thespindle. Ball bearings 54, 56 intervene between the spindle bushings 42,44 and the headstock bushings 53, 60, which latter bushings 58, 60 haveinterior diameter permitting longitudinal movement of the threadedsleeve 36 therein. Hence the headstock spindle unit, comprising thespindle 32, sleeve 3S, bushings 42, 44, pulley 43 and center 28, canmove in axial directions and does so move when the unit is rotated, dueto coaction of the threaded sleeve 36 with a nut 62 xed interiorly ofthe headstock.

The particular master-thread sleeve t herein represented is designed foruse in cutting the threads on tappet valves of aircraft engines. Sleeveswith different threads and corresponding nuts are interchangeable forthe sleeve 35 and nut 62.

Rotation of the spindle unit, at a suitably slow speed, is accomplishedby a reversible electric motor 64 which drives a shaft 66 throughsuitable reduction gears 68. A pulley 7|] on shaft 66 has a V-belt 12connecting it with the spindle pulley 48. The V-belt engaging incorresponding peripheral grooves in the pulleys, permits the pulley 48to move axially with the spindle the required amount in each directionwithout breaking the drive connection and while the motor 64, shaft B6and pulley 'I9 remain relatively iixed in positions.

The tailstock spindle 34 is shown in detail in Fig. 4. It has a portion74 of enlarged diameter whose upper part is formed as a gear rack 76 forcoacting with a, spur gear 'I8 which rotates with a short shaft 80mounted transversely of the tailstock. Shaft 8U extends out through thefront wall of the tailstocl: and has on its outer end a handle 82 bywhich the gear may be manually rotated to move the spindle axially indirection away from the work. As represented, a spring pressed lingerpin 84 rides on a plane surface 8S of the tailstock as the handlerotates. One or more holes 83 in said plane surface may be provided inwhich said pin may engage, to maintain the spindle temporarily in aparticular position.

Referring to Fig. 4, the tailstock spindle 34 has the bushings 93, 92press-fitted or otherwise mounted thereon, on opposite sides of theenlarged portion 74, and ball bearing units 94, 92 intervene betweenthese bushings 99, S2 and tail stock bushings 98, I which latter aremounted nxedly within the tailstock. Preferably, the exterior diameterof the spindle bushings 93, 92 will be at least equal to the externaldiameter of the enlarged portion 'I4 of the spindle so that thisenlarged portion can pass through the ring of ball bearings S6 to permitinsertion and removal of the spindle when the end cap |82 is removed.

The inner-center-carrying end of tailstcck spindle 34 may be connectedto the tailstock by a protective flexible cover or boot |04, of leatheror the like, to keep metal chips and other foreign matter frominterfering with the free sliding movement or the spindle.

The axial position of spindle 34 in the tailstock is determined by theposition of spindle 32 in the headstock, through a, flexibleinterconnection between them. As representd in Fig. 4, a long coilspring |06 is housed within an axial bore |08 in the tailstock spindle34, seating at its inner end f on the bottom of the bore and engaging,at its outer end, a plug or piston IIl which is slidable in the bore |08and which is controlled as to position by a lever I I2.

The lever II2 has its lower end pivotally mounted at I|4 on the outerend of a pin or stud I|6 which is adjustably xed on the base member I4as by being threaded into the base member and locked by the lock nut I8.

The upper free end of lever I I2 is bifurcated as at |23 (Fig. 5), and arelatively short large diameter pin |22 is rotatably mounted in alignedopenings |24, extending across the space between the spaced end.portions of the lever. This short large diameter pin |22 has screwedtherein a relatively long smaller diameter pin |26 whose inner endprojects into an axial cavity |28 in the plug or piston IIi, with itsend bearing on a ball |43 in the bottom of the cavity. Hence the leverII2 may be swung in one direction about its pivot II4 thereby to forcethe plug or piston III) inward for applying pressure to spring Ii andthrough it to the spindle 34, and may be swung in the opposite directionto relieve the spring and spindle of lever pressure.

Intermediate its ends', the lever H2 is formed with a yoke portion |32,the side walls of which have aligned openings |34 for mounting rotatablya large diameter pin |36, similar to the pin |22. This pin |35 has atransverse hole |38 loosely receiving the threaded end of a connectingrod |40, and nuts |42 on the outer end of the rod maintain the rodagainst pulling out cf pin |38 and alsov permit adjustment of theeiTective length of the rod between lever I i2 and a similar lever |44to which the opposite end of the rod is connected at the headstock endof the machine.

Referring to Fig. 1, the connecting rod |43 is a straight and stiff rodextending loosely through the base member I4. Its connection to lever|44 is similar to its connection at the opposite end to lever H2, leveridd being pivoted at ist o-n the outer end of a pin, or stud, |48 whichis threaded into base member |13 and adjustable therein by the lock nut|i3. The connecting rod extends loosely through a large diameter pini552 rotatably mounted at the yoke part 54 of the lever, with a nut |58screwed on the outer end of the connecting rod to prevent its pullingout of pin |52.

Lever it, like lever |52, is bifurcated at its free end for rotatablymounting the large diameter pin |53 in which a long smaller diameter pinitil is threaded with its inner end engaging a ball |52 in the bottom ofa cavity ifofi formed in the end of the headstock spindle 32.

Hence, by adjusting the nut ist, at the head'- stock end oi theconnecting rod Util, or the nuts M32 at the tailstock en the lever i l2may be drawn inward against the resiliency of spring tot, or may bepermitted to be moved outward by the spring accordingly as the effectivelength of the connecting rod is shortened or lengthened by suchadjustment.

Threads are out in the work held between the centers il@ by a grindingwheel |65 which is belt driven by an electric mo-tor |68. The wheel |56may be moved into and out oli thread grinding relation to the work byany suitable means such as is disclosed and claimed in our copendingapplication for patent Serial No. 539,357, led June 8, 1944.

In operation, assuming that the work is a valve tappet whose exteriorsurface is to be threaded,

the headstock and tailstock will be suitably spaced apart and xed inpositions on the base mem ber le. Assuming the spindles to be at thelimit oi their travel to the left, a movement of the tailsto-ck handleS2 counter-clockwise will retract the tails-took spindle Sli to enablethe insertion of a valve tapp-et between the centers 2.9, 3b, afterwhich release of handle 32 will result in move ment or spindle 35i intoengagement with the work, under the inuence of spring iil, and

the pressure exerted axially on the work will be f a proper pressurepredetermined by adjustment of the effective length of the connectingrod |46.

The grinding wheel 36 may be continuously rotating while the work isbeing inserted and removed from the machine but will be backed away fromthread cutting position at such times. When the valve tappet, or otherpiece of work, has been engaged between the centers 28, Sii, the wheelit will be advanced to thread-cutting position. Then the switch |1i3 atthe front of the machine will be turned clockwise to its R position tostart motor titi operating in direction to move the spindles 32, 3d andthe work held between their centers to the right, through the medium ofthe threaded sleeve 36 on the headstock spindle, coacting with the iiXednut 52 in the headstock. The V-belt spindle drive permits the spindlepulley 68 to move with the spindle the needed amount.

When the rotating tappet has moved axially an amount sunicient to havethreads cut alo-ng a predetermined extent thereof, the spindle drivingmotor te automatically stops. By employing a suitably over-long threadedsleeve 35 in the headstock, the work may be removed and a new pieceinserted at this limit of movement to the right, precisely as describedat the other limit. However, the illustrated machine is designed to makea rough cut on its movement to the right and a nish cut as the same workpiece moves 6 back to its left hand limit of travel. Hence, at the righthand limit, the operator merely moves the wheel forward for the finishout and turns v switch |153 to its L position. When the threaded workpiece comes to rest at its left hand limit of travel, the grinding wheelwill be backed away as before, and handle 32 manually rotated counter-clockwise to release the threaded piece and to permit insertion ofan unfinished piece in line with the centers, after which the handle 2is released and spring iil presses the spindle 3ft inward until itscenter 39 engages the work with the predetermined axial pressure. WheelLES is next moved forward to its position for a rough cut, after whichswitch |1il is turned clockwise to its R position to start motor etoperating in direction to move the work to the right past the grindingwheel.

The automatic stopping of motor Sri to limit travel oi the work to rightand to left is accomplished by a pair of micro switches |12, |16 mountedin a casing |15 on the front of the headstock 1S. The switches aresuitably spaced apart in direction of travel of the spindles, and eachswitch has an actuator |18, |85 projecting toward the other switch. Anarm |82 is mounted within casing |16 between the switches |12, |115, itbeing secured on a slidable rod Hifi. Oppositely disposed screws |86,|88 are adjustable in the arm 82 and are aligned respectively with theactuator |18, |536, so that, when the arm |82 moves to the right, screwi8@ engages the actuator |18 to open the motor circuit and, when the arm|82 moves to the left, screw |88 similarly engages actuator |35 to openthe motor circuit.

As represented, the arm |82 has its end which is remote from rod |85grooved as at l@ for riding on a guide plate |92.

Movement of arm |82 to right and left is accomplished by the pulley 138as it moves with the h'eadstock spindle 32. A lever IQ@ depends from apivot |36 within the casing |98 at the front of the headstock, and thelever carries a pair of rollers 29%3, 252 disposed on opposite sides ofthe pulley d8. A link connection 2|!!! between lever |94 and rod lflcauses sliding movement of the rod when lever ldd swings about its pivot|96 as a result of engagement of pulley i8 with one or the other ofrollers 2130, 202. Hence, when pulley d8 moves to the right, rod |84 ismoved to the right until screw |86 engages actuator |18 to stop motor6d. Similarly, the rod moves to the left when the pulley so moves, untilscrew |88 engages actuator |8 to stop the motor. However, each actuator|18, moves out to its original closed circuit position as soon as thescrew |88 or |88 moves away, thereby conditioning the system for manualcontrol at the switch ITB at the front of the machine. The electricalsystem controlled by the micro switches |12, |14 and the manual switch|18 is shown diagrammatically in Fig. l2.

Referring now to Fig. l2, the manual switch |1' is shown in its Lposition closing lines 2 and 3 through the solenoid 205 whoseenergization will attract switch arm '2Ei8 and close the three phasecircuit to reversible motor E@ by operation of the gang of switches atthe left of the motor. Hence the motor will operate in direction to movethe work from right to left until 7 open the motor circuit. However, themomentum of the rotor of the motor might cause over-running of the workunless counter-acted. Hence provision is made for momentarily reversingthe current through the motor for braking the rotor. The reversal of thecurrent does not persist long enough to actually reverse the travel ofthe rotor but has the effect of stopping the rotor almostinstantaneously. This result is accomplished by means of a timer 2Wcontrolling a normally closed switch 2M in a circuit through a solenoid2|6 which circuit is normally open at the microswitch actuator |80.When, however, the actuator |80 is actuated to open the operating motorcircuit, it closes the circuit through solenoid 2|6 whose energizationresults in closing the switch unit 2|8 thereby to energize the solenoid229 at the right of motor 64. Switch arm 222 is attracted by solenoid22|! to the right thereby closing the associated gang of switches andclosing the reversing circuit through the motor. Timer 2|0, however, maybe set to operate on three to ve cycles and opens its switch 2M to openthe reversing circuit before actual reversal of the motor Bil occurs.The action is similar when arm |82 moves to the right and opens actuator|18 of micro-switch |74. Movement to the right will be preceded by ashifting of switch |'||l to its R' position thereby to causeenergization of the solenoid 220. A motor 224 of a coolant distributingsystem 226 may be plugged into the regular motor circuit at will.

We claim as our invention:

1. In a machine tool, a headstock spindle and a tailstock spindle, saidspindles having centers between which the work is held, means mountingsaid spindles for movement in axial directions, means associated withthe headstock spindle constraining it against axial movement, resilientmeans urging the tailstock spindle axially toward the headstock spindle,said resilient means including a pair of pivoted levers respectively atthe outer end of the headstock spindle and at the outer end of thetailstock spindle, the headstock lever engaging the outer end of theheadstock spindle and there being a. spring intervening between thetailstock lever and the tailstock spindle, said levers having aconnectingvrod preventing relative spreading apart of the levers andpermitting relative movement of said levers toward each' other, andmeans on the connecting rod for adjusting its effective length betweenthe levers.

2. In a machine tool, a headstock spindle and a tailstock spindle, saidspindles having centers between which the work is held, means mountingsaid spindles for movement in axial directions, means associated withthe headstock spindle constraining it against axial movement, resilientmeans urging the tailstock spindle axially t0- ward the headstockspindle, said resilient means including a pair of pivoted leversrespectively at the outer end of the headstock spindle and at the outerend of the tailstock spindle, th'e headstock lever engaging the outerend of the headstock spindle and there being a spring interveningbetween the tailstock lever and the tailstock spindle, said levershaving a connecting rod preventing relative spreading apart of thelevers and permitting relative movement of said levers toward eachother, and means for adjusting the tension of said spring between thetailstock lever and the tailstock spindle, thereby to vary the springpressure tending to move the tailstock spindle toward the h'eadstockspindle.

BENJAMIN S. T. BISHOP. FRANK A. BICKNELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,311,815 Briney Feb. 23, 19432,317,226 Seyferth Apr. 20, 1943 2,347,766 Briney May 2, 1944 1,367,523Bernard Feb. 1, 1921 1,528,188 Frost Mar. 3, 1925

